Re: [ofa-general] Re: [patch 5/6] mmu_notifier: Support for drivers with revers maps (f.e. for XPmem)

Nick Piggin
2008-02-26T09:23:09Z

On Tuesday 26 February 2008 18:21, Gleb Natapov wrote:
> On Tue, Feb 26, 2008 at 05:11:32PM +1100, Nick Piggin wrote:
> > > You are missing one point here. The MPI specifications that have
> > > been out there for decades do not require the process use a library
> > > for allocating the buffer. I realize that is a horrible shortcoming,
> > > but that is the world we live in. Even if we could change that spec,
> >
> > Can you change the spec?
>
> Not really. It will break all existing codes.

I meant as in eg. submit changes to MPI-3

> MPI-2 provides a call for
> memory allocation (and it's beneficial to use this call for some
> interconnects), but many (most?) applications are still written for MPI-1
> and those that are written for MPI-2 mostly uses the old habit of
> allocating memory by malloc(), or even use stack or BSS memory for
> communication buffer purposes.

OK, so MPI-2 already has some way to do that... I'm not saying that we
can now completely dismiss the idea of using notifiers for this, but it
is just a good data point to know.

Thanks,
Nick